The major objective is to identify putative microbial etiologic agents in SLE and RA by methods based on nucleic acid hybridization and related techniques. DNA from blood or tissue of patients with these disorders will be examined in this way. Secondary goals relate to investigating more proximate pathogenetic mechanisms in these diseases, using similar techniques, as well as to using any information so-derived for immediate clinical application where possible. In this regard studies will be continued into the use of synthetic DNA antigens for examining anti-DNA antibodies more extensively as well as to further explore the clinical and pathological significance of circulating DNA.